1. Field of the Invention
The present invention relates to an optical waveguide for widespread use in optical communications, optical information processing, and other general optics.
2. Description of the Related Art
An optical waveguide is incorporated in an optical device such as an optical waveguide device, an optical integrated circuit, an optical wiring board and the like, and is widely used in the field of optical communications, optical information processing, and other general optics. In general, the optical waveguide includes cores serving as a passageway for light and formed in a predetermined pattern, and an under cladding layer and an over cladding layer formed so as to cover the cores (see, for example, JP-A-2005-165138). Such an optical waveguide is shown in FIG. 6. In FIG. 6, an under cladding layer 2, cores 3, and an over cladding layer 4 are formed in the order named on a substrate 1 to form the optical waveguide.
The refractive index of the above-mentioned cores 3 is made higher than that of the under cladding layer 2 and the over cladding layer 4 so that light passing inside the cores 3 does not exit from the cores 3. The cores 3, the under cladding layer 2 and the over cladding layer 4 are in general made of a synthetic resin. In particular, when the cores 3, the under cladding layer 2 and the over cladding layer 4 are made of a photosensitive resin, the formation thereof involves the need for the steps of coating, exposure to light, development and drying of liquid materials therefor.
However, the execution of the above-mentioned steps of coating, exposure to light, development and drying for each of the processes of forming the cores 3, the under cladding layer 2 and the over cladding layer 4 described above requires a large number of processing steps to result in the increase in costs. In this regard, there is room for improvement.